Screw Compressor for a Utility Vehicle

ABSTRACT

A screw compressor for a utility vehicle has an air filter with an intake port and an air supply channel for supplying air to the screws of the screw compressor. The intake port is arranged between the air filter and the air supply channel and includes a pocket groove which can maintain the oil.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a screw compressor for a utility vehicle, having an air filter, having an inlet connector and having an air feed channel for the feed of air to the screws of the screw compressor.

Screw compressors for utility vehicles are already known from the prior art. Such screw compressors are used to provide the compressed air required for the brake system of the utility vehicle, for example.

In this context, in particular oil-filled compressors, in particular also screw compressors, are known, in the case of which it is necessary to regulate the oil temperature. This is generally realized by virtue of an external oil cooler being provided which is connected to the oil-filled compressor and to the oil circuit via a thermostat valve. Here, the oil cooler is a heat exchanger which has two mutually separate circuits, wherein the first circuit is provided for the hot liquid, that is to say the compressor oil, and the second circuit is provided for the cooling liquid. As cooling liquid, use may for example be made of air, water mixtures with an antifreeze, or another oil.

This oil cooler must then be connected to the compressor oil circuit by means of pipes or hoses, and the oil circuit must be safeguarded against leakage.

This external volume must furthermore be filled with oil, such that the total quantity of oil is also increased. The system inertia is thus increased. Furthermore, the oil cooler must be mechanically accommodated and fastened, either by means of brackets situated in the surroundings or by means of a separate bracket, which necessitates additional fastening means and also structural space.

U.S. Pat. No. 4,780,061 has already disclosed a screw compressor with an integrated oil cooling arrangement.

Furthermore, DE 37 17 493 A1 discloses a screw compressor installation which is arranged in a compact housing and which has an oil cooler on the electric motor of the screw compressor.

A generic screw compressor is already known for example from DE 10 2004 060 417 B4.

It is the object of the present invention to advantageously further develop a screw compressor for a utility vehicle of the type mentioned in the introduction, in particular such that the oil management of a screw compressor for a utility vehicle can be simplified and improved.

This object is achieved according to the invention by a screw compressor for a utility vehicle equipped with an air filter, an inlet connector and an air feed channel for the feed of air to the screws of the screw compressor. The inlet connector is arranged between the air filter and the air feed channel and has a pocket groove by which oil can be retained.

The invention is based on the underlying concept of a pocket being integrated into the inlet connector, which pocket can retain oil after the compressor has been or is deactivated and ventilated. It is the intention for said oil to then be drawn into the compressor interior again upon the restart of the compressor. In particular, it is the intention to prevent oil from entering the air filter in the region of the inlet or air inlet of the screw compressor. Through the provision of a pocket groove, the oil can be collected and retained, wherein it is however also made possible at the same time for said oil to be drawn into the screw compressor from said pocket groove.

Furthermore, provision may be made for the pocket groove to be of encircling form. In this way, a uniform inflow of oil into the pocket groove is made possible. The manufacturing process is also simplified in this way.

Provision may furthermore be made for the pocket groove to be designed and configured such that oil can flow into and collect in the pocket groove owing to the influence of gravitational force. This may be achieved in particular by virtue of the orientation of the pocket groove in the assembled state or operating state being such that the air filter is above the inlet connector and the air feed channel is below the inlet connector, and oil that precipitates on the inlet connector runs down the walls into the pocket groove.

Provision may furthermore be made for the pocket groove to be designed and configured such that oil can be drawn from the pocket groove into the compressor interior upon the start-up of the screw compressor. In particular, in this context, provision may be made for the depth of the pocket groove, or that part of the pocket groove which faces toward the air feed channel, to be designed such that, as it is drawn in, the oil can be drawn out of the pocket groove.

Provision may furthermore be made for the inlet connector to be a separate component. In this context, provision may be made in particular for the base of the pocket groove to be formed for example by an encircling sealing ring or the like. The oil that precipitates in the interior of the inlet connector and nms down thus runs in the direction of the seal and collects on the base of the pocket groove. From there, it can then be drawn out again upon the start-up.

Further details and advantages of the invention will now be discussed in more detail on the basis of an exemplary embodiment illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional drawing through a screw compressor according to the invention; and

FIG. 2 shows a perspective sectional drawing through the inlet connector of the screw compressor as per FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a schematic sectional illustration, a screw compressor 10 in the context of an exemplary embodiment of the present invention.

The screw compressor 10 has a fastening flange 12 for the mechanical fastening of the screw compressor 10 to an electric motor (not shown in any more detail here).

What is shown, however, is the input shaft 14, by which the torque from the electric motor is transmitted to one of the two screws 16 and 18, specifically the screw 16.

The screw 18 meshes with the screw 16 and is driven by means of the latter.

The screw compressor 10 has a housing 20 in which the main components of the screw compressor 10 are accommodated.

The housing 20 is filled with oil 22.

At the air inlet side, an inlet connector 24 is provided on the housing 20 of the screw compressor 10. The inlet connector 24 is in this case designed such that an air filter 26 is arranged at said inlet connector. Furthermore, an air inlet 28 is provided radially on the air inlet connector 24.

In the region between the inlet connector 24 and the point at which the inlet connector 24 joins to the housing 20, there is provided a spring-loaded valve insert 30, which is designed here as an axial seal.

This valve insert 30 serves as a check valve.

Downstream of the valve insert 30, there is provided an air feed channel 32 which feeds the air to the two screws 16, 18.

At the outlet side of the two screws 16, 18, there is provided an air outlet pipe 34 with a riser line 36.

In the region of the end of the riser line 36, there is provided a temperature sensor 38 by means of which the oil temperature can be monitored.

Also provided in the air outlet region is a holder 40 for an air deoiling element 42.

In the assembled state, the holder 40 for the air deoiling element has the air deoiling element 42 in the region facing toward the base (as also shown in FIG. 1).

Also provided, in the interior of the air deoiling element 42, is a corresponding filter screen or known filter and oil separation devices 44, which will not be specified in any more detail.

In the central upper region in relation to the assembled and operationally ready state (that is to say as shown in FIG. 1), the holder for the air deoiling element 42 has an air outlet opening 46 which leads to a check valve 48 and a minimum pressure valve 50. The check valve 48 and the minimum pressure valve 50 may also be formed in one common combined valve.

The air outlet 51 is provided downstream of the check valve 48.

The air outlet 51 is generally connected to correspondingly known compressed-air consumers.

In order for the oil 22 that is situated and separated off in the air deoiling element 42 to be returned again into the housing 20, a riser line 52 is provided which has a filter and check valve 54 at the outlet of the holder 40 for the air deoiling element 42 at the transition into the housing 20.

A nozzle 56 is provided, downstream of the filter and check valve 54, in a housing bore. The oil return line 58 leads back into approximately the central region of the screw 16 or of the screw 18 in order to feed oil 22 thereto again.

An oil drain screw 59 is provided in the base region, in the assembled state, of the housing 20. By means of the oil drain screw 59, a corresponding oil outflow opening can be opened, via which the oil 22 can be drained.

Also provided in the lower region of the housing 20 is the attachment piece 60 to which the oil filter 62 is fastened. Via an oil filter inlet channel 64, which is arranged in the housing 20, the oil 22 is conducted firstly to a thermostat valve 66.

Instead of the thermostat valve 66, it is possible for an open-loop and/or closed-loop control device to be provided by means of which the oil temperature of the oil 22 situated in the housing 20 can be monitored and set to a setpoint value.

Downstream of the thermostat valve 66, there is then the oil inlet of the oil filter 62, which, via a central return line 68, conducts the oil 22 back to the screw 18 or to the screw 16 again, and also to the oil-lubricated bearing 70 of the shaft 14. Also provided in the region of the bearing 70 is a nozzle 72, which is provided in the housing 20 in conjunction with the return line 68.

The cooler 74 is connected to the attachment piece 60, as will be discussed in more detail below in FIGS. 2 to 4.

In the upper region of the housing 20 (in relation to the assembled state), there is situated a safety valve 76, by means of which an excessively high pressure in the housing 20 can be dissipated.

Upstream of the minimum pressure valve 50, there is situated a bypass line 78, which leads to a relief valve 80. Via said relief valve 80, which is activated by means of a connection to the air feed 32, air can be returned into the region of the air inlet 28. In this region, there may be provided a ventilation valve (not shown in any more detail) and also a nozzle (diameter constriction of the feeding line).

Furthermore, approximately at the level of the line 34, an oil level sensor 82 may be provided in the outer wall of the housing 20. Said oil level sensor 82 may for example be an optical sensor, and may be designed and configured such that, on the basis of the sensor signal, it can be identified whether the oil level during operation is above the oil level sensor 82 or whether the oil level sensor 82 is exposed, and thus the oil level has correspondingly fallen.

In conjunction with this monitoring, it is also possible for an alarm unit to be provided which outputs or transmits a corresponding error message or warning message to the user of the system.

The function of the screw compressor 10 shown in FIG. 1 is as follows.

Air is fed via the air inlet 28 and passes via the check valve 30 to the screws 16, 18, where the air is compressed. The compressed air-oil mixture, which, having been compressed by a factor of between 5 and 16 downstream of the screws 16 and 18, rises through the outlet line 34 via the riser pipe 36, is blown directly onto the temperature sensor 38.

The air, which still partially carries oil particles, is then conducted via the holder 40 into the air deoiling element 42 and, if the corresponding minimum pressure is attained, passes into the air outlet line 51.

The oil 22 situated in the housing 20 is kept at operating temperature via the oil filter 62 and possibly via the heat exchanger 74.

If no cooling is necessary, the heat exchanger 74 is not used and is also not activated.

The corresponding activation is performed by means of the thermostat valve 66. After purification in the oil filter 62, oil is fed via the line 68 to the screw 18 or to the screw 16, and also to the bearing 70. The screw 16 or the screw 18 is supplied with oil 22 via the return line 52, 58, and the purification of the oil 22 takes place here in the air deoiling element 42.

By means of the electric motor (not shown in any more detail), which transmits its torque via the shaft 14 to the screw 16, which in turn meshes with the screw 18, the screws 16 and 18 of the screw compressor 10 are driven.

By means of the relief valve 80 (not shown in any more detail), it is ensured that the high pressure that prevails for example at the outlet side of the screws 16, 18 in the operational state cannot be enclosed in the region of the feed line 32, and that, instead, in particular during the start-up of the compressor, there is always a low inlet pressure, in particular atmospheric pressure, prevailing in the region of the feed line 32. Otherwise, upon a start-up of the compressor, a very high pressure would initially be generated at the outlet side of the screws 16 and 18, which would overload the drive motor.

FIG. 2 shows, in a perspective sectional illustration, the inlet connector 24 of the screw compressor 10 as per FIG. 1.

As already shown in conjunction with FIG. 1, the inlet connector is arranged between air filter 26 and air feed channel 32. The inlet connector 24 furthermore has a pocket groove 100 by which oil can be retained.

Here, the pocket groove 100 is of encircling form.

A sealing ring 104 is situated in the base 102 of the pocket groove 100.

The inlet connector 24 is formed as a separate component, and the sealing of the gap between the inlet connector 24 and the boundary of the air feed channel 32 is realized by means of the sealing ring 104.

The pocket groove 100 is designed and configured such that oil can flow into the pocket groove 100 and collect there owing to the influence of gravitational force.

Oil is drawn out of the pocket groove 100 into the compressor interior upon the start-up of the compressor 10.

LIST OF REFERENCE DESIGNATIONS

-   10 Screw compressor -   12 Fastening flange -   14 Input shaft -   16 Screws -   18 Screws -   20 Housing -   22 Oil -   24 Inlet connector -   26 Air filter -   28 Air inlet -   30 Valve insert -   32 Air feed channel -   34 Air outlet pipe -   36 Riser line -   38 Temperature sensor -   40 Holder for an air deoiling element -   42 Air deoiling element -   44 Filter screen or known filter or oil separation devices -   46 Air outlet opening -   48 Check valve -   50 Minimum pressure valve -   51 Air outlet -   52 Riser line -   54 Filter and check valve -   56 Nozzle -   58 Oil return line -   59 Oil drain screw -   60 Attachment piece -   62 Oil filter -   64 Oil filter inlet channel -   66 Thermostat valve -   68 Return line -   70 Bearing -   72 Nozzle -   76 Safety valve -   78 Bypass line -   80 Relief valve -   82 Oil level sensor -   100 Pocket groove -   102 Base -   104 Sealing ring 

1-5. (canceled)
 6. A screw compressor for a utility vehicle, comprising: an air filter; an inlet connector; and an air feed channel for feeding air to screws of the screw compressor, wherein the inlet connector is arranged between the air filter and the air feed channel, and the inlet connector has a pocket groove by which oil is retained.
 7. The screw compressor as claimed in claim 6, wherein the pocket groove is of encircling form.
 8. The screw compressor as claimed in claim 7, wherein the pocket groove is configured such that oil is flowable into and collectable in the pocket groove owing to influence of gravitational force.
 9. The screw compressor as claimed in claim 6, wherein the pocket groove is configured such that oil is flowable into and collectable in the pocket groove owing to influence of gravitational force.
 10. The screw compressor as claimed in claim 6, wherein the pocket groove is configured such that oil can be drawn out of the pocket groove into an interior of the compressor upon start-up of the compressor.
 11. The screw compressor as claimed in claim 6, wherein the inlet connector is a separate component. 